Charging system for a car

ABSTRACT

A surge voltage produced by intermittent operation of a voltage regulating device 5 is suppressed by providing a second power source 10 for exciting an alternating current generator.

CROSS REFERENCE TO CO-PENDING APPLICATIONS

Reference is made to co-pending applications having the same inventorsas the present application, namely Ser. No. 576,388 filed 1-27-84 andSer. No. 576,390 filed 1-27-84.

FIELD OF TECHNOLOGY

The present invention relates to a charging device for a car having acharging generator.

BACKGROUND OF TECHNOLOGY

FIG. 1 is a circuit diagram showing one example of the conventionalcharging device for a car. In the figure, the reference numeral 1designates the armature coil of an alternating current generator mountedon a car and so on (not shown) to be actuated by an internal combustionengine (not shown); 2 designates a field coil provided near the armaturecoil 1; 3 designates a main rectifying devie for rectification of thearmature coil; 4 designates an auxiliary rectifying device; 5 designatesa voltage regulating device for controlling voltage between outputterminals of the main rectifying device 3 to be a predetermined value bycontrolling a field current; 6 designates a battery; 7 designates akey-switch connected in a circuit comprising the battery 6, the fieldcoil 2 and the voltage regulating device 5; 8 designates a pilot lampplaced in the vicinity of the key-switch 7 to indicate chargingcondition of the battery, one terminal of the pilot lamp being connectedto the key-switch and the other being connected to the junction betweenthe voltage regulating device 5 and the auxiliary rectifying device 4;and 9 designates an electrical load connected in parallel to the battery6.

The operation of the conventional device constructed as above-mentionedwill be described.

When the engine is in stopped condition, closing of the key-switch 7flows an initial field current in a circuit of the battery 6→key-switch7→a pilot lamp 8→field coil 2→voltage regulating device 5→battery 6 withthe result that a field ampere-turn is produced in the field coil 2. Atthe same time, the pilot lamp 8 is lightened to indicate that thebattery 6 is not in charging. Under the condition as above-mentioned,when the engine is started by a starting motor, a voltage is induced inthe armature coil 1 since the armature coil is excited. When therotating speed of the engine, that is, the alternating current generatorreaches a predetermined value, the field current is supplied through theauxiliary rectifying device 4 and the voltage regulating device 5whereby the alternating current generator acts as a self-excitedgenerator. Namely, a circuit for field current of the auxiliaryrectifying device 4→field coil 2→voltage regulating device 5→ground→mainrectifying device 3→auxiliary rectifying device 4 is formed. Further,when the output voltage of the auxiliary rectifying device 4 reaches apredetermined level, the field current is interrupted by the voltageregulating device 5 with the result that the output voltage of theauxiliary rectifying device 4, namely the output voltage of the mainrectifying device 3 is kept at a predetermined level. At the same time,the pilot lamp 8 is extinguished to indicate that the battery 6 is incharging.

However, in the conventional device above-mentioned in which a fieldcurrent is supplied from the output of the generator, particularly of acontrol system in which a voltage is controlled to become apredetermined level by intermittence of the field current, there appearsintermittence of the load in the output of the generator for an amountcorresponding to the field current whereby a high surge voltage isproduced across output terminals of the rectifier as shown in FIG. 2when the field current is interrupted, namely the voltage regulatingdevice 5 is actuated. Occurrence of the surge voltage became a principalcause of noise. In FIG. 2, the symbol B designates surge voltage at thetime of commutation in the generator.

SUMMARY OF THE INVENTION

According to the present invention, variation of a surge voltage causedby intermittent actuation of a voltage regulating device is suppressedby providing a power source for exciting an alternating currentgenerator independent of a battery and supplying a field current to afield coil through the power source for excitation whereby occurrence ofnoise is effectively reduced.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a circuit for the conventional charging device for a car;

FIG. 2 is a diagram showing the waveform of a surge voltage in theconventional device;

FIG. 3 is a circuit diagram of an embodiment of the present invention;and

FIG. 4 is a diagram similar to FIG. 2 of an embodiment of the presentinvention.

PREFERRED EMBODIMENT OF THE INVENTION

FIG. 3 is a circuit diagram of an embodiment of the charging device fora car according to the present invention.

In FIG. 3, the reference numeral 10 designates a second battery as apower source for exciting an alternating current generator (not shown)and the positive side is connected in series to the voltage regulatingdevice 5 above-mentioned through the field coil 2. 11 designates a powersource such as a solar battery, a thermo-electric conversion element andso on which is used to charge the second battery; 12 designates areverse current blocking diode whose anode is connected to the powersource and whose cathode is connected to the positive side of the secondbattery 10. 13 designates a second key-switch which opens and closes insynchronism with the key-switch 7 and which is connected between thefield coil 2 and the junction of the battery and the reverse currentblocking diode 12.

The operation of the embodiment of the present invention having theconstruction above-mentioned will be described.

First of all, when the key-switch 7 and the second key-switch 13 aresimultaneously closed under non-operating condition of the engine, aclosed circuit of the battery 6→key-switch 7→pilot lamp 8→voltageregulating device 5→battery 6 is formed and the pilot lamp 8 islightened by conductive current to indicate that the battery 6 is not incharging.

Simultaneously, a closed circuit of the second battery 10→secondkey-switch 13→field coil 2→voltage regulating device 5→second battery 10is formed by the second battery 10 which has been charged by the powersource 11 through the diode 12 whereby a field current flows in thefield coil 2 to cause a field ampere-turn. Under the condition asabove-mentioned, when the engine is started by a starting motor (notshown), voltage is induced in the armature coil 1. When the voltagereaches a predetermined level, the electric current to the pilot lamp 8is stopped and the pilot lamp 8 is extinguished to indicate that thebattery 6 is in charging. Further, when the output voltage of thevoltage regulating device 5 reaches a predetermined level, the fieldcurrent is interrupted by the voltage regulating device 5 and the outputvoltage of the auxiliary rectifying device 4, namely the output voltageof the main rectifying device 3 is kept at a predetermined level. Thus,intermittence of the field current to render an output voltage to be apredetermined level does not cause change in the load of the generatorsince the field current is supplied through the second battery 10 asdescribed above. Therefore, the surge voltage C is not resulted even atthe time of interruption of field current as found in the surge voltagewaveform of FIG. 4.

In the embodiment as above-mentioned, description has been made as tothe second battery being charged by the solar battery and so on. Thesame effect as in the embodiment can, however, be attained by using agenerator for excitation instead of the solar battery.

INDUSTRIAL UTILITY

The present invention is applicable not only to an alternating currentgenerator for a vehicle but also to a car such as farm tractor, anindustrial vehicle and so on.

We claim:
 1. A charging system for a car which suppresses surge voltagesin the output, comprising:A generator having an armature coil forproducing an alternating output and a field coil facing said armaturecoil; a rectifying device for rectifying said alternating output toproduce a rectified output voltage; a voltage regulating device forcontrolling said rectified output voltage by controlling the fieldcurrent in said field coil; a battery charged with the rectified outputfrom said generator; a first switch for connecting said voltageregulating device and said battery; a power source independent of saidbattery and independent of said rectified output voltage, connected toone side of said field coil for supplying the entire field current tosaid field coil; and a second switch mechanically connected to saidfirst switch so as to be operated concurrently therewith, said secondswitch connecting said power source to said field coil; wherein theoperation of said voltage regulating device does not produce a surgevoltage in said rectified output.
 2. The charging system for a caraccording to claim 1, wherien said power source includes a secondbattery and a solar battery and said second battery is charged by saidsolar battery.
 3. The charging system for a car according to claim 1,wherein said power source includes a second battery and athermo-electric conversion element and said second battery is charged bysaid thermo-electric conversion element.